Engine exhaust emission regulations are becoming increasingly restrictive. Over the years engineers have discovered that engine exhaust emissions can be significantly reduced at certain operating conditions by providing a particular injection flow rate identified by a rate trace. In many cases engine exhaust emissions are improved when the initial injection flow rate of the fuel injector is controlled. Prior rate trace techniques are concerned with modifying the slope associated with the linear portion of the rate trace by providing a slower injection pressure rise versus time. The slower rise improves emissions at start up and low idle conditions by injecting less fuel into the combustion chamber compared to full load conditions. While these techniques have some ability to reduce emissions, there remains room to improve the rate trace at the start of injection.
Another problem, fuel consumption is becoming more of an operational expense. Over the years, engineers have discovered that engine fuel consumption is significantly improved at certain operating conditions by providing a particular injection flow rate identified by a rate trace. In many cases fuel consumption can be improved during the early phase of the combustion process. In many cases engine fuel consumption is improved when the initial injection flow rate of the fuel injector is controlled. Prior rate trace techniques are concerned with modifying the slope associated with the linear portion of the rate trace by providing a slower injection pressure rise versus time. The slower rise improves fuel consumption at start up and low idle conditions by injecting less fuel into the combustion chamber compared to full load conditions. While these techniques have some ability to reduce fuel consumption, there remains room to improve the rate trace at the start of injection.
Yet another problem, engine noise is becoming increasingly restrictive. Over the years, engineers have discovered that engine noise can be significantly reduced by injecting the fuel slower during the early phase of the combustion process where combustion is less harsh. In many cases engine noise is improved when the initial injection flow rate of the fuel injector is controlled. Prior rate trace techniques are concerned with modifying the slope associated with the linear portion of the rate trace by providing a slower injection pressure rise versus time. The slower rise improves engine noise at start up and low idle conditions by injecting less fuel into the combustion chamber compared to full load conditions. While these techniques have some ability to reduce engine noise, there remains room to improve the rate trace at the start of injection.
The present invention is directed to overcoming one or more of the problems as set forth above.